Cosmetic deodorants are preparations which mask, remove, or decrease perspiration odors, prevent their development, or do all of these. Many such products which have a satisfactory deodorant efficacy and cosmetic characteristics appear on the market each year.
In order to control objectionable odors of perspiration, it is necessary either to check the flow of excess perspiration or to eliminate its odor, or both.
A variety of substances which have astringent action inhibit the flow of perspiration. The mechanism by which such antiperspirants act has not been clearly defined.
Salts of metals such as aluminum, iron, chromium, lead, mercury, zinc, and zirconium have astringent properties which may be demonstrated by protein precipitation. However, some of these, because they produce discoloration, and others, because of possible toxic effects, are not suitable for cosmetic preparations. Salts of aluminum and zinc are those most commonly used. The astringency of these salts is also dependent on the anion. Sulfate, chloride, chlorhydroxide, and phenolsulfonate have been most widely used, although basic formate, lactate, sulfamate, and the alums are also found in antiperspirant products. Acetates are generally unsatisfactory because of odor. At the acid pH necessary for astringency, the acetic acid odor is very definite and is a difficult one to cover. Formates are to be avoided since they tend to produce skin sensitization. Aluminum salts are generally used in concentrations of 12 to 20%. Tannins and tannic acid have been used as antiperspirants.
The aluminum compound that has been most widely used in antiperspirant compositions is aluminum chlorhydroxide complex. Commonly referred to as aluminum chlorhydrate or aluminum chlorhydroxide, the product is a 5/6 basic aluminum chloride complex with the atomic ratio of aluminum to chlorine of 2:1. In dry form it is a glass-like rather than a crystalline substance, readily soluble in water. A 20% solution has a pH of approximately 4.2 with good buffering capacity. It is not irritating or sensitizing to normal skin and causes little or no damage to fabrics. The concentration recommended for use in antiperspirant products is 20%. Aluminum chlorhydrate complex is sold under a variety of trade names, dry in granular or powdered form, or as a 50% solution. The solution is stable and remains clear with little change in pH over long periods of standing. The solid is insoluble in 95% ethyl alcohol, but the 50% solution is miscible in all proportions with 95% ethyl alcohol. (S. Plechner, Cosmetics: Science and Technology, Vol. 2, Balsam et al Ed, John Wiley & Sons, Inc., 1972, p. 375).
Antiperspirants appear in several physical forms. The most popular forms are creams, lotions, sticks, powders, and liquids.
Clear roll-on lotions may be prepared using an aqueous alcohol solution of such thickeners as methyl cellulose or hydroxyethyl cellulose in a concentration of 0.4 to 0.7% with aluminum chlorhydroxide 18 to 20%. S.D. 40 alcohol may be used at 15 to 20%. Addition of small amounts of humectant and emollient prevents formation of aluminum salt crystals on the ball and improves the feel of the product on the skin. A nonionic emulsifier will be needed to disperse the perfume.
The final viscosity of a roll-on-type product should be established before a package is selected. The amount of clearance between the ball and fitment will depend on the viscosity of the product. If the lotion is too thin, it will drip and run as it is applied. If it is too thick, it will be scraped off on the fitment as the ball turns and will feel wet after application. The exact viscosity desired and the amount to be applied will vary with the kind of thickener used in the lotion and with the astringent selected. (Plechner, p. 391).
Antiperspirants have also been developed in stick form. A type of antiperspirant stick is made from a solidified alcohol gel composition. A combination of an astringent chloride with a hard wax dissolved by heating in alcohol will form a solid gel on cooling. Addition of a higher fatty acid or an ester improves the texture and rigidity of the product. (Plechner, p. 392).
Patent literature reveals an antiperspirant stick comprising a sodium stearate-aqueous alcohol gel base with sodium zirconium lactate as the antiperspirant agent.
Patent literature further reveals an alcohol-sodium stearate gel antiperspirant stick containing aluminum hydroxide as the active antiperspirant agent. The use of isopropyl palmitate or isopropyl myristate as a physical stabilizer is also revealed. (Plechner, p. 394).
The soap-gel sticks in general are not as effective as a well-formulated antiperspirant cream or lotion. However, they have reasonably good astringency and constitute a convenient form of application.
It is an object of this invention to provide a gelled antiperspirant which will keep the active ingredient in uniform suspension. It is a further object to provide a gelled antiperspirant with a suitable dispensing viscosity for roll-on application. It is still a further object to provide a gelled antiperspirant that holds the active ingredient in a residual film on the skin and has a longer lasting effect.